I think all too often we perceive ourselves as being 'buddies' with the landowners and convince ourselves that we're helping them out and doing them management favours - when in all actuality, the landowners or farmers really just see the tenants as a means of generating a few extra quid and a 'nice to have' resource to have when the pigeons flatten his crops in the summer. - however, I think tenants are a lot more disposable than they/we like to think. Sadly...
80% rise though, I'd say you ask him why and see if he can actually justify it, then either agree/accept or decline - after all, it's a business contract like all others.